1. Field of the Invention
This invention relates to improvements in insulation for a refractory shield in high temperature industrial furnaces. More particularly, this invention relates to insulated suspended furnace walls in which metallic hangers for mounting a refractory shield are effectively cooled by exposure to a cooling fluid, while the exterior face of the refractory shield is effectively insulated to reduce energy requirements for high temperature industrial furnaces.
2. Description of the Prior Art
High temperature industrial furnaces are typically lined with a refractory material. Occasionally a flat roof is required, or relatively long open slots must be provided in the furnace walls for feeding a charge into the furnace. In such cases, it is necessary to suspend and tie back the refractory material to a structural framework. In high temperature furnaces, such as glass manufacturing furnaces, it is desirable to direct a cooling fluid over the metallic suspension or tie-back means to reduce the average temperature of the suspension or tie-back means and thereby prolong their service life. Suspension and tie-back means typically comprise cast metallic pieces which may deteriorate and crack when subjected to extended exposure at high temperatures.
The desirability of cooling the exterior side of the refractory wall and the metallic hangers has been recognized by prior art. U.S. Pat. No. 3,045,994 suggests cooling the furnace wall, i.e., the refractory shield, as well as the metallic hangers therefor by passing an airstream upwardly along the furnace wall and providing lateral apertures in the hanger castings to facilitate the air flow. This approach, while providing some cooling of the metallic hangers, is unsatisfactory since the airstream is warmed by prior contact with the lower portion of the furnace wall, and because the airstream moves at a relatively slow rate. U.S. Pat. No. 3,139,486 teaches that direct impingement of a concentrated cooling air blast onto a refractory furnace wall is undesirable, since such impingement causes holes and/or cracks to develop in the furnace wall.
U.S. Pat. No. 3,812,798, the teachings of which are incorporated by reference herein, teaches a mounting means for a suspended refractory shield which comprises a support means providing structural support for the refractory shield; a hollow, tubular hanger tube depending from the support means; a plurality of substantially Y-shaped metallic hanger means and/or shelf hanger means engaging the hanger tube and adapted to engage and hold refractories forming the refractory shield; and a cooling fluid supply means communicating with an open end of the hanger tube and providing cooling fluid through oblong openings in the hanger tube directly cooling the metallic hanger means mounted on the hanger tube. This suspended wall design has proven very successful, and the present invention relates to improvements thereto.